1. Field of the Invention
The present invention relates to a heating device, and more specifically, relates to a heating device for heating a wafer to be used as a substrate in a manufacturing process of a semiconductor device or heating other plate-like heating object.
2. Description of the Related Art
In a manufacturing process of a semiconductor device, heating treatment is implemented for forming an insulating film and the like on a wafer by using a semiconductor manufacturing apparatus. Among heating devices for heating the wafer in this semiconductor manufacturing apparatus, there is a heating device that includes a disc-like ceramic base having a heating surface for mounting the wafer thereon and heating the wafer, in which a heating element is provided in the ceramic base. This heating device is applied not only to a deposition step in the semiconductor manufacturing process but also advantageously to a surface treatment step of performing dry etching for a surface of the wafer by a plasma atmosphere and the like, and to the like.
In the deposition step and surface treatment step of the wafer, a heating temperature of the wafer and temperature uniformity in the surface of the wafer affect properties of a coated film deposited on the wafer and properties of the etched surface of the wafer, and as a result, affect characteristics and yield of the semiconductor device. Hence, it is required that heating of the heating device be controlled so that the wafer can be heated uniformly in the surface thereof at a predetermined temperature at the time of the deposition step of the wafer and the time of the surface treatment step thereof.
Accordingly, among such heating devices in each of which the heating element is provided in the ceramic base, there is a heating device, in which resistance heating elements are embedded individually in a central portion and a peripheral portion in an inside of the ceramic base, and it is possible to control heat generation of the resistance heating element in the central portion of the ceramic base and heat generation of the resistance heating element in the peripheral portion thereof independently of each other.
With regard to the heating device as described above, there is a multizone resistance heater, in which a first heating element is disposed in a first plane in an inside of a body of a stage, and a second heating element is disposed in a second plane more apart from a surface of the stage than the first plane in the inside of the body of the stage (Japanese Patent Laid-Open Publication No. 2003-59848).
Moreover, there is a heating device, in which, in the same plane in the base, the first heating element is provided in the peripheral portion of the heater, and the second heating element is provided in the central portion of the heater (Japanese patent Laid-Open Publication No. 2003-133195).
However, in the heating device as described in Japanese Patent Laid-Open Publication No. 2003-59848, in which the first heating element and the second heating element are provided in the different planes in the base, the heating elements are embedded in the two different layers in the base, and accordingly, the number of manufacturing steps of the heating device is increased, and a disadvantage has been brought from a viewpoint of productivity. Moreover, since the base is thickened, a heat capacity of the base is increased, and there is an apprehension that thermal responsiveness thereof when the temperature rises and drops may be decreased.
Moreover, in the heating device as described in Japanese Patent Laid-Open Publication No. 2003-133195, in which, in the same plane in the base, the first heating element is provided in the peripheral portion of the heater, and the second heating element is provided in the central portion of the heater, with regard to a temperature distribution from the central portion of the base to such an outer circumferential portion thereof, a temperature distribution in which a temperature change is extremely large is prone to occur, and a large thermal stress sometimes occurs in the base. In particular, when this base is made of ceramics, there has been an apprehension that a breakage may occur therein owing to the large thermal stress.
This invention has been made in order to advantageously solve the above-described problems. It is an object of this invention to provide a heating device capable of uniformly heating the base without increasing the thickness of the base or without increasing the thermal stress that occurs in the base.